Tropical Storm Ernesto Discussion Number   6
NWS National Hurricane Center Miami FL       AL052024
1100 PM AST Mon Aug 12 2024

Ernesto remains a rather broad tropical cyclone, and satellite and 
radar data shows that deep convection has yet to 
consolidate/concentrate near its center. Tonight's NOAA P-3 TDR data 
in Ernesto also suggests the broad center currently lacks much 
vertical alignment.  However, there are a number of convective 
banding features around the circulation and the overall organization 
of the cloud pattern has been increasing since earlier today.  
Satellite imagery shows that the upper-level anticyclonic outflow 
pattern is well defined over the western semicircle of the 
circulation.  The intensity is held at 35 kt for this advisory based 
on observations from Air Force and NOAA reconnaissance aircraft and 
Dvorak satellite estimates.

Since the system is still in the formative stage, there is some 
scatter in the center position estimates, making the initial motion 
estimate somewhat uncertain.  My best motion estimate is generally 
westward at a slightly slower speed, around 275/22 kt.  During the 
next day or so, a mid-level ridge to the north of Ernesto should 
maintain a westward to west-northwestward motion at a gradually 
decreasing forward speed.  This should take the center of the 
tropical cyclone over portions of the Leeward Islands very soon, 
across the extreme northeastern Caribbean Sea on Tuesday, and near 
or over portions of Puerto Rico Tuesday evening or Tuesday night.  
After that, the flow on the eastern side  a deep-layer trough moving 
off the U.S. east coast should cause Ernesto turn northward to 
north-northeastward.  Later in the forecast period, the first trough 
that steers the system northward from the Greater Antilles leaves 
Ernesto behind, and the tropical cyclone may have to wait for a 
second trough to steer it farther into the mid-latitudes.  The 
official track forecast is near the left edge of the guidance suite 
during the first 24-36 hours and close to the simple model consensus 
from 2-5 days.  

Assuming that deep convection will increase near the center of 
Ernesto, the high-level outflow and otherwise conducive oceanic and 
atmospheric environment favors strengthening during the next few 
days.  Although the intensification is expected to be gradual during 
the early part of the period, a more rapid rate of strengthening is 
likely after the system moves north of the Greater Antilles.  The 
official intensity forecast is about the same as the previous one 
and close to the multi-model consensus.


Key Messages:

1. Ernesto is expected to bring tropical storm conditions to
portions of the Leeward Islands beginning early Tuesday and to the
Virgin Islands and Puerto Rico by late Tuesday. Tropical Storm
Warnings are in effect for this entire area.

2. Heavy rainfall may result in locally considerable flash flooding
and mudslides in areas of the Leeward and Virgin Islands through
Wednesday, and over Puerto Rico late Tuesday into Thursday.

3. It is too soon to know what impacts Ernesto could bring to
Bermuda late this week, and interests there should monitor the
progress of this system.


FORECAST POSITIONS AND MAX WINDS

INIT  13/0300Z 16.0N  59.6W   35 KT  40 MPH
12H  13/1200Z 16.4N  62.0W   40 KT  45 MPH
24H  14/0000Z 17.7N  64.6W   50 KT  60 MPH
36H  14/1200Z 19.5N  66.5W   60 KT  70 MPH
48H  15/0000Z 21.7N  67.8W   70 KT  80 MPH
60H  15/1200Z 24.0N  68.3W   80 KT  90 MPH
72H  16/0000Z 26.1N  67.7W   90 KT 105 MPH
96H  17/0000Z 29.9N  65.3W   95 KT 110 MPH
120H  18/0000Z 32.7N  64.2W   95 KT 110 MPH

$$
Forecaster Pasch